The founder of the Akao school, Akao Jinzaemon 赤尾甚左衛門
, was originally from the Umetada school in Yamashiro Province. He moved to Fukui around the Kan'ei period (circa 1630), and for several generations, his family served as official craftsmen for the Fukui domain, producing works that displayed a unique and resilient character not found in other schools.

This work is characterized by finely forged steel with a purplish-brown rust surface. It features intricate openwork design such as cloves, shippō (seven treasures), cherry blossoms, Kara-hana (Chinese flowers), mokkō (four-lobed flowers), and plum blossoms. The two Hitsu-ana (holes for kozuka and kogai) were adorned with raised plum branches and a double-layered diamond pattern of Nikai-hishi design.

Mid-Edo period